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<pre class="textdiagram" id="fig49">
     Cluster 1          :          Cluster 2
                        :
                        :
+---+  +---+            :             +---+  +---+
| C |  | C |            :             | C |  | C |
+-+-+  +-+-+    +----+  :  +-----+    +-+-+  +-+-+
  |      |      |    |  :  |     |      |      |
  |      |      |    |  :  |     |      |      |
+-+------+------+-+  |  :  |   +-+------+------+-+
|     Broker      |  |  :  |   |     Broker      |
+-+------+--------+  |  :  |   +--------+------+-+
  |      |      ^    |  :  |     ^      |      |
  |      |      |    |  :  |     |      |      |
+-+-+  +-+-+    |    +-----------+    +-+-+  +-+-+
| W |  | W |    |       :  |          | W |  | W |
+---+  +---+    +----------+          +---+  +---+
                        :
</pre>
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